Review the risks

News that a long-term study of Canadian women disputes the benefit of routine mammography screening for women at low risk of breast cancer gives good reason for those older than 50 to have a serious talk with their physicians.

Cancer Care Manitoba advises women between 50 and 74 years of age to have a mammogram every two years, and it is not altering that recommendation.

The followup 25 years after a trial involving almost 90,000 Canadian women has critics questioning the value, underscored by the potential harm, of screening at any age women who are not at high risk of breast cancer. The authors said they found no difference in mortality rates between women who had the mammography screens and those who didn't.

Mammography, with its lower dose of radiation, gave hope decades ago for detecting breast cancer and cutting death rates because it can detect smaller spots than the lumps found in physical exams, allowing for earlier diagnosis. But as the evidence of its benefits has developed, enthusiasm has waned.

As risks become clearer and proof of benefit pared back, some see little or no use in screening.

There is significant chance of "over-diagnosis," with women being treated for cancers that will never become lethal.

Cancer Care Manitoba follows the lead of a national task force that evaluates the often-conflicting data from medical studies.

It stands by its opinion mammography in older women cuts the breast cancer death rate. (Women of high risk often bypass mammography for MRI screening at younger ages.)

The agency notes this study, among eight the task force weighs, is the only one concluding routine screening does not reduce mortality rates.

The national study has added valuable data on the risk of over-diagnosis. Cancer Care wants to study the incidence of over-diagnosis in Manitoba for a clearer picture.

It is this risk that women at low risk need to weigh in discussion with their physician.

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